After returning from work I noticed that the computer running WDisplay was unresponsive. So I restarted it, everything came up fine but after 10 mins or so it became unresponsive again. Restarted it again and I noticed, that data hadn't been updated since the night before ... at around the time Mint had offered me a new kernel which of course I had installed. restarted it again and chose the kernel everything had worked before.

But again, after a couple of minutes the computer became unresponsive again. Another restart and I kept an eye on RAM usage and I could see that RAM was eaten up very fast.

It took me a while to realize, that around the same time I had installed the new kernel my Netatmo for whatever unrelated reason had stopped sending data. After restarting it everything went back to normal.

I assume that would be Weatherdisplay ... under normal conditions it uses around 50% of RAM (which is the reason, why I restart it by a script every 6 hours). It simply surprised me, that within a couple of minutes all RAM was gone, because the Netatmo "decided to hang" ...